Field
The present teachings relate to optical fibers in general and in particular, to single-mode and multi-mode holey fibers having large core dimensions and devices and systems that use such fibers such as lasers and amplifiers.
Description of the Related Art
A holey fiber is an optical fiber where optical guidance is provided by an arrangement of “holes” disposed about a core. Such holes may have a refractive index lower than that of the core, and collectively form a cladding region having an effective refractive index also lower than that of the core.
More generally, holey fiber is used herein to refer to fiber comprising a plurality of cladding features, e.g., holes, disposed in a matrix, wherein the cladding features may have a refractive index different from that of the matrix. Accordingly, light incident on the cladding features may be reflected or scatter therefrom.
A photonic crystal fiber (PCF) is a holey fiber where the holes are arranged in a regular manner. In one arrangement, the cladding region can be formed by holes arranged in a hexagonal close-packing-like manner, and the core can be formed in the center area of such hexagonal patterned cladding region. The core can be in the center area where a center hole, and one or more inner “rings” of holes, would otherwise be located in the extended array of holes. PCFs formed in the foregoing manner thus have a core dimension and a cladding region thickness.
As with traditional fibers, sustained propagation of only a single mode in PCFs is desirable in many applications. Conventional PCFs operable in the single-mode propagation regime have core dimensions and cladding region thicknesses that resemble traditional non-holey single-mode fibers. One limitation of such single-mode traditional fibers and conventional PCFs is that the core dimension is limited to a relatively small value. In such small core fibers, high optical power levels result in peak intensities that induce non-linearities in the properties of the core and fiber. High power application of such fibers, therefore, is either not practical or not possible.